Which is true?
A. Protons attract other protons.
B. Electrons determine the atom's size.
C. Most of an atom's volume is filled with matter.
D. Protons repel electrons.

Dr. Jones says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. Jones that ...

Which statement is true of the energy levels of electrons in shells?

A. Electrons must lose energy to move from the first to the second shell.
B. The valence shell has higher energy than other occupied shells.
C. All the electrons in an atom have similar amounts of energy.

An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________.

An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have ...

Which statement is most useful in explaining why chemists assign atoms to chemical elements by counting protons?
A. The nucleus doesn't change in stable isotopes.
B. The proton's negative charge holds electrons in the atom.
C. Protons at the atom's surface determine the atom's behavior.
D. 99% of the atom's mass consists of protons.
E. None of these. Elements are defined by the number of proton

Consider a hypothetical atom with an atomic number of 4 and a net electronic charge of +1. How many neutrons does this atom have?

The answer cannot be determined by that information. Correct
All the atoms of an element have the same number of protons, but some atoms have more neutrons than other atoms of the same element and therefore have more mass. Without the mass number (number of protons + neutrons), it is not possible to determine the number of neutrons.